The present invention relates generally to batteries for use with an implantable medical device (IMD). More particularly, the present invention pertains to an integral housing of an implantable medical device for containing a formable flat battery.
As implantable medical device (IMD) technology advances in an attempt to address a myriad of life sustaining/enhancing needs, issues such as IMD battery longevity, IMD size and shape, IMD mass, and patient comfort remain key considerations in the IMD design process. Much attention is typically placed on the power source of an implantable medical device during the IMD design process. It is appreciated that battery size and capacity, for example, significantly impact the physical configuration of the IMD and the duration of service time within the patient before battery replacement is required.
A conventional approach to providing power within an implantable medical device involves the use of a self-contained battery, not unlike a common battery which is commercially available to the consumer. Such a self-contained battery includes active electrochemical cell components housed in a battery can. Battery housing connectors or contacts are provided for establishing electrical connections to circuitry disposed within in the implantable medical device.
It is well appreciated in the IMD manufacturing industry that the battery component of an IMD requires the allocation of an appreciable percentage of usable space within the IMD. It can be appreciated that reducing the size of the battery is a desirable design objective. However, reducing IMD battery size results in a corresponding reduction in battery capacity, which necessarily places limits on the ability to make significant battery size reductions using conventional IMD battery design principles.
Moreover, the can of a conventional IMD battery is often of a configuration that creates xe2x80x9cdead spacexe2x80x9d within the implantable medical device (e.g., a can having a substantially square or rectangular shape). Although a thoughtful design approach can help to reduce the amount of such dead space, an appreciable volume of space within the IMD typically remains unusable when employing a conventional IMD battery. Also, the metal battery can that contains the active battery components must be of a thickness sufficient to protect against battery leakage. The thickness of the battery can must also be taken into consideration when allocating space within the IMD to house a battery source of a conventional design.
There is a need in the implantable medical device manufacturing community for an IMD battery implementation which provides for an overall reduction in IMD size without a corresponding reduction in battery capacity. There exists a further need for an IMD battery implementation that provides enhanced flexibility in terms of shape, size, and other form factor properties. The present invention fulfills these and other needs.
The present invention is directed to a selectable deformable housing assembly for an implantable medical device (IMD). An IMD housing according to the present invention includes a first shell and a second shell. The first and second shells include an inner surface and an outer surface, respectively. The outer surfaces of the first and second shells are fabricated from a material compatible with body fluids. The implantable medical device further includes a battery enclosure defined by a cover and all or a portion of the first shell of the IMD housing. The cover of the battery enclosure is disposed between the inner surfaces of the first and second shells and has a greater thickness dimension or higher modulus of elasticity than the first shell. An electrochemical battery cell, such as a flat liquid electrolyte battery, is provided in the battery enclosure. Electronic circuitry, supported on a flexible wiring substrate, which is electrically coupled to the electrochemical battery cell and a medical electrical lead, is provided between the inner surface of the second shell and the cover of the battery enclosure. A hermetic seal is provided between the cover of the battery enclosure and the applicable portion of the first shell.
The deformable housing assembly is further defined by a feedthrough assembly, which couples the battery to the electronic circuitry. The feedthrough assembly is disposed within a hermetically sealed aperture of the cover and includes a ferrule and a feedthrough pin that are isolated from one another.
The electrochemical battery cell is further defined to include a lithium anode, a cathode with Li/CSVO/CFx chemistry and a liquid electrolyte of type 1M LiBFy in GBL/DME.
The hermetic seal provided between the cover of the battery enclosure and the first shell is preferably a weld joint. In one embodiment, the battery enclosure cover includes a coined edge and the hermetic seal is established by a butt weld joint between the coined edge of the cover and a peripheral edge of the first shell.
According to another embodiment of the present invention, a housing assembly for an implantable medical device includes a housing comprising a first shell and a second shell, with the outer surfaces of the first and second shells including a material compatible with body fluids. The first shell includes a spanked edge. A battery enclosure is defined by a cover and at least a portion of the first shell of the IMD housing. The cover of the battery enclosure is situated between the inner surfaces of the first and second shells, has a greater thickness dimension or higher modulus of elasticity than the first shell, and includes a peripheral edge. A hermetic seal, according to this embodiment, is established by a spank weld joint between the peripheral edge of the cover and the spanked edge of the first shell.
The first shell may further include a first substantially straight peripheral wall portion and a second substantially straight peripheral wall portion adjacent to the first portion and offset from the first portion to form a ledge, which the peripheral edge of the cover engages. The hermetic seal is established by a spank weld joint between the peripheral edge of the cover and the spanked edge of the first shell.
According to yet another embodiment, the cover may also include a substantially straight peripheral wall portion. The hermetic seal is established by a standing edge weld joint between the substantially straight peripheral wall portion of the cover and the substantially straight peripheral wall portion of the first shell.
The present invention is also directed towards a method for assembling a battery into a housing assembly for an IMD including the following steps: providing a shallow drawn case; providing a battery cover having a greater thickness or higher modulus of elasticity than the case; coupling a cathode to the cover; glassing a feedthrough assembly having a feedthrough tube disposed within a ferrule to electrically isolate the feedthrough tube from the ferrule and to bond the feedthrough tube to the ferrule; hermetically sealing the ferrule of the feedthrough assembly to the cover; coupling a feedthrough pin to an anode current collector; placing an insulator tube over the feedthrough; placing the cover over the anode current collector while directing the feedthrough pin through the feedthrough tube; coupling the feedthrough pin to the feedthrough tube; and hermetically sealing the cover to the case.
The above summary of the present invention is not intended to describe each embodiment or every implementation of the present invention. Advantages and attainments, together with a more complete understanding of the invention, will become apparent and appreciated by referring to the following detailed description and claims taken in conjunction with the accompanying drawings.